The argument that Working Memory (WM) is especially important for reading comprehension has been supported in previous research. The aim of this study was to test a non-computerized WM training method to improve children’s reading comprehension in a longitudinal design. 38 Danish children in 3rd and 4th grade (M = 112.9 months, SD = 7.90 months) were divided into a training group (N = 18) and a control group (N = 20). Assessments of sentence reading comprehension and WM were administered at pre- and post-test, half-year and one-year follow-up. Verbal WM and reading comprehension were not improved following training. Visuo-spatial WM improved at post-training, but the effect did not last into the one-year follow up. The role of WM in reading comprehension and the pedagogical implications for teaching are discussed.